The present invention relates to variable displacement compressors that are used in vehicle air conditioners. More particularly, the present invention relates to an improvement of a housing for a control valve in the external control variable displacement.
U.S. Pat. No. 5,865,604, which corresponds to Japanese Unexamined Patent Publication No. 8-338364, describes a variable displacement compressor that the displacement is controlled by the pressure difference between the pressure in the control chamber and the pressure in the suction chamber. The displacement of the compressor is controlled by supplying refrigerant gas to the control chamber from the discharge chamber via a supply passage and releasing the gas into the suction chamber via a bleed passage. A displacement controlling structure of the compressor includes an electrically operative control valve in the passageway of the supply passage, which alters the size of an area of the supply passage. An energized solenoid of the control valve urges a valve body of the control valve toward the direction in which a valve hole closes. The value of the supplied current to the control valve is decided based on the comparison between predetermined temperature and detected temperature of a passenger compartment. A large difference between the detected temperature detected by a temperature sensor and the predetermined temperature set by a temperature controller indicates that cooling load is greatly needed. This causes the opening amount of the valve hole to become smaller. Thus, the inclination of a swash plate increases, and the discharge capacity of the compressor increases.
As shown in FIG. 5, an electrically operative control valve 80 is accommodated in a valve chamber 85 defined in a rear housing 90. The valve chamber 85 has an opening surrounded by a circumferential wall or a base portion 86 protruding from an outer circumferential wall surface of the rear housing 90. The base portion 86 forms annularly and an inner circumferential surface 87 of the base portion 86 has an annular recess 88. A circular clip 89 is fitted to the recess 88, by which prevents the control valve 80 from falling out of the valve chamber 85. A connector 81, a center of which protrudes outwardly, is arranged on the base portion and is provided with a connection assembly 82 to which an electrical power supply line 83 to energize the solenoid (not shown) is electrically connected. The power supply line 83 is covered with a cover 91 which protects the power supply line 83.
The control valve 80 is generally installed to the rear housing 90 and protrudes its end outwardly from the outer circumferential wall of the rear housing 90. This projection causes to hinder from installing a compressor to an object. Particularly, mounting a compressor on a vehicle as a part of air conditioner, a mounting space is restricted and the control valve 80 is required to reduce the projection from the outer circumferential wall of the rear housing 90.
According to the prior compressor, the connection assembly 82 of the connector 81 is set back from the base portion 86 toward the valve chamber 85. This arrangement of the connection assembly 82 frequently causes the power supply line 83, which connects an external drive circuit to the connection assembly 82, to contact with a periphery of the base portion 86. However, the prior compressor is only designed to define the valve chamber 85 to accommodate the control valve 80 and is not assumed the power supply line 83 to be in contact with the periphery of the base portion 86. Therefore, the periphery of the base portion remains edged.
Meanwhile, the power supply line 83 is protected by the cover 91, but the cover 91 does not protect until the connection assembly of the power supply line 83. A certain length of the uncovered power supply line 83 is necessary for electrical connecting to the connector 81. In other words, the power supply line 83 is not protected by the cover 91 in order to secure the efficiency of the connecting work.
When the uncovered power supply line 83 contacts with a periphery of the base portion, long-term vibration of the compressor and an engine to which the compressor is installed cause the contact surface of the power supply line 83 to wear out.
The present invention contemplates to alleviate the above-mentioned inconveniences. Accordingly, it is an object of the present invention to provide an external control variable displacement compressor which is capable of preventing an electrical power supply line of an electrically operative control valve from wearing out.
To achieve this object, an external control variable displacement compressor has a housing, a control chamber defined in the housing and an electrically operative control valve accommodated in the housing to control pressure in the control chamber. The displacement of the compressor is varied based on the pressure in the control chamber. The control valve controls the pressure in the control chamber due to an external electrical signal. A valve chamber which is defined in the housing has an opening to accommodate the control valve and an agonic surface formed at the opening. An electrical power supply line connected to the control valve is in contact with the agonic surface. According to the present invention, when the power supply line is in contact with the opening of the valve chamber, the agonic surface supports the power supply line, which prevents the power supply line from wearing out.
Furthermore, the present invention has such a feature that the agonic surface is formed on a part of a circumferential wall surrounding the opening.
Furthermore, the present invention has a following feature that the circumferential wall formed along the valve chamber opening protrudes from an outer circumferential wall surface of the housing and the projection of the agonic surface from the outer circumferential wall surface of the housing is less than the rest of the circumferential wall. According to the present invention, even if the circumferential wall protrudes from the outer circumferential wall surface, contact stress of the power supply line against the circumferential wall becomes smaller than that of the prior compressor.